JPH06118394A - Liquid crystal composite film - Google Patents

Abstract

PURPOSE:To provide a liquid crystal composite film which has a good phase sepn. structure and can attain the high turbidity state in a thin film and consequently a high contrast by constituting the liquid crystal composite film of a high-polymer material consisting of an ion polymer of cyclic ether, more preferably a polymer having specific polyoxethane skeleton in at least a part and a liquid crystal material. CONSTITUTION:This liquid crystal composite film is constituted of the high- polymer material consisting of the ion polymer of the cyclic ether, more preferably the polymer having the polyoxethane skeleton expressed by formula in at least a part and the liquid crystal material. In the formula, R<1>, R<2> are the same or different org. groups; (n) is the degree of polymn. The high polymer having such polyoxethane skeleton is generally obtd. by the ring opening polymn. of a 4-membered cyclic ether compd. The ring opening polymn. is effected by a cation polymn. using a Lewis acid catalyst. As a result, the composite film structure having the good phase sepn. structure is created and the high contrast is attained with the thin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel liquid crystal composite film used for display materials, light control materials and the like.

[0002]

2. Description of the Related Art There are various types of liquid crystal composite films composed of a polymer material and a liquid crystal material, depending on the method of forming the liquid crystal film. Those in which a liquid crystal is encapsulated (Fergason, Japanese Patent Publication No. 58-501631).
Liquid crystal is deposited in a granular form by thermal curing of the oligomer (Doane, Japanese Patent Publication No. 61-502128), and liquid crystal is deposited in a granular form by photo-curing of the oligomer (Vaz, JP-A-62-2231). Issue bulletin).

On the other hand, a liquid crystal composite film obtained by applying a uniform solution of a polymer material and a liquid crystal material consisting of their common solvent and evaporating the solvent was first reported by Kajiyama et al. In 1979 (Chem. lett. 679 (1979)). It has been reported that the liquid crystal composite film has a structure in which a continuous phase of a sponge-like matrix polymer having a three-dimensional network structure is filled with a liquid crystal material in a continuous phase in a three-dimensional network form ( J. Appl. Polym. Sci. 29, 3955 (1984)). Also,
The electro-optical response of the liquid crystal composite film due to solvent evaporation is
-501512 and Japanese Patent Laid-Open No. 1-230693.

In a liquid crystal display device in which the liquid crystal composite film is sandwiched between a pair of conductive substrates, incident light is scattered because the liquid crystal molecules in the pores are in a random state when no voltage is applied. The membrane remains opaque. When a voltage is applied to the pair of conductive base materials sandwiching the composite film, Δε> 0 [where Δε is the dielectric anisotropy,
formula:

[0005]

[Equation 1]

It is represented by

[0007]

[Outer 1]

Is the dielectric constant in the molecular axis direction,

[0009]

[Outside 2]

Indicates the dielectric constant in the direction orthogonal to the molecular axis. )], If the liquid crystal molecules are aligned in the direction of the electric field and the refractive index n _{p of the} polymer and the ordinary refractive index n _{o of the} liquid crystal are substantially the same, incident light can pass through the composite film without being scattered. Thus, the composite film exhibits an electro-optical effect of converting it into a transparent state. Since such a liquid crystal composite film can form a composite film having the above-mentioned electro-optical effect only by applying and drying a solution in which a polymer material and a liquid crystal material are dissolved, it is possible to increase the area of the liquid crystal display element. There is an advantage.

[0011]

The liquid crystal composite film obtained by applying and drying the solution as described above uses an acrylic or methacrylic resin as a polymer material with a few exceptions. This is also due to the transparency of acrylic or methacrylic resins, the matching of the refractive index with the liquid crystal, and the economic efficiency, but the major reason is that it is easier to form a microscopically phase-separated composite film structure. is there. Other materials, such as fluororesins and silicone resins, have a low affinity with the liquid crystal and it is difficult to obtain a good phase-separated structure, so that there is a problem that the contrast (white turbid state) deteriorates.

Further, since the phase separation between the liquid crystal and the polymer is induced by the difference in the molecular weight, it is desirable that the molecular weight of the polymer is high. However, ordinary acrylic or methacrylic resin is synthesized by radical polymerization. However, since the molecular weight distribution is wide, it is unavoidable that there is a considerable amount of low molecular weight components that adversely affect the phase separation. Further, the composite film is formed by evaporation of the solvent, but in order to obtain a good phase separation structure, it is necessary to use a solvent having a low boiling point and high volatility, such as dichloromethane, chloroform, dichloroethane, acetone, etc. Since polymeric materials must be soluble in their solvent, they limit the choice of polymeric materials.

Therefore, a main object of the present invention is to provide a liquid crystal composite film having a good phase separation structure and capable of achieving a strong opaque state (high contrast) in a thin film.

[0014]

Means and Actions for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned objects, and as a result,
A liquid crystal composite film composed of a polymer material composed of an ionic polymer of cyclic ether and a liquid crystal material forms a better phase separation structure than a liquid crystal composite film using a conventional acrylic or methacrylic resin, and is a thin film. It was found that a strong white turbid state (high contrast) can be achieved, and the present invention has been completed.

Examples of the ionic polymer of the cyclic ether include those having a polyoxetane skeleton represented by the following general formula in at least a part thereof.

[0016]

[Chemical 2]

(In the formula, R ¹ and R ² are the same or different organic groups, and n is the degree of polymerization.) Such a polymer having a polyoxetane skeleton is generally a four-membered ring represented by the following general formula. Obtained by ring-opening polymerization of an ether compound. The ring-opening polymerization is performed by cationic polymerization using a Lewis acid catalyst (for example, Takeo Saegusa, Lecture Polymerization Reaction Theory <6>, Ring-Opening Polymerization (I), Kagaku Dojin, 1971).
Issued annually, pp. 153-162).

[0018]

[Chemical 3]

(In the formula, R ¹ and R ² are the same as above.) The resulting polymer has a strong living polymerizability, has a high molecular weight and has a very narrow molecular weight distribution in many cases. As a polymer having a polyoxetane skeleton, poly 3,3-bis (chloromethyl) oxetane has been commercially available from Hercules (USA) under the trade name of “Penton” (Penton).

Since the polyoxetane skeleton has an ether type oxygen atom in the main chain, it has a characteristic that the main chain has high flexibility as compared with acrylic or methacrylic resins and other vinyl polymers. Specific examples of the substituents R ¹ and R ² include, in addition to hydrogen atom, a linear alkyl group having 1 to 20 carbon atoms such as methyl group and ethyl group; 3 to 20 carbon atoms such as isopropyl group and t-butyl group. A branched alkyl group; a halogen-substituted alkyl group having 1 to 20 carbon atoms in the alkyl portion such as a chloromethyl group and a bromomethyl group; an alkoxyalkyl group such as a methoxymethyl group and a 2-methoxyethyl group; a hydroxymethyl group, a cyanomethyl group Groups containing polar groups such as (for example, the number of carbon atoms in the alkyl moiety is 1
~ 20 hydroxyalkyl groups or cyanoalkyl groups) and the like.

By introducing into the substituents R ¹ and R ^{2 a} group having a relatively long molecular chain (for example, a straight-chain alkyl group having 4 to 20 carbon atoms), the crystallinity of the polymer is reduced to make it amorphous. It is possible to improve the quality of the liquid crystal, increase the affinity of the liquid crystal, and have a high molecular weight and a narrow molecular weight distribution. High contrast can be achieved with a thin film.

Substituent R¹, R²A polar group (hydroxyl group, shear
Of the polymer itself, the dielectric constant of the polymer itself
Increase the liquid crystal drive voltage of the liquid crystal composite film.
It is possible to However, in the monomer
The presence of polar groups hinders cationic polymerization, resulting in a high degree of polymerization.
Therefore, it is difficult to protect the polar group with a protecting group during polymerization.
It is preferable to protect it. For example, in the case of hydroxyl group,
Silylating agent [for example (C ₂H_Five)₃Cyril by SiCl etc.
After being polymerized and polymerized, it is hydrolyzed back to hydroxyl groups.
The law can be adopted.

In order to obtain a good phase-separated structure, in order to enhance the affinity with the liquid crystal, at least one of R ¹ and R ² has a methylene chain-(CH ₂ ) _m- (where m is 1 to It is appropriate to provide a part (which is an integer of 12). Also, the methylene chain-
An ether group oxygen atom may be introduced by bonding an alkoxyl group to the terminal of (CH ₂ ) _m −. The polymer material used may be a copolymer composed of two or more kinds of monomers, or a mixture of two or more kinds of homopolymers. The weight average molecular weight (M _w ) is preferably 100,000 or more, and the molecular weight distribution (M _w / M _n ) is 2 or less, more preferably 1.5 or less.

When at least one of R ¹ and R ² contains a skeleton unit which is a group partially having a hydroxyl group (such as a hydroxymethyl group) and is crosslinked by a crosslinking agent capable of reacting with the hydroxyl group, the molecular weight is Since it becomes larger and the phase separation from the liquid crystal becomes more clear, heat resistance can be imparted. Examples of the cross-linking agent include polyisocyanate, diisocyanate, polyepoxy and diepoxy.

As the above-mentioned liquid crystal material, various commonly used liquid crystal materials can be used. The ratio of the polymer material / liquid crystal material is appropriately determined according to the type of each material used, but it is preferable that the weight ratio is usually within the range of 1/9 to 6/4. In order to obtain a liquid crystal display device or the like using the liquid crystal composite film of the present invention, a solution in which each of the above components is dissolved is applied onto one transparent electrode and dried and solidified to form a composite film as in the conventional case. After that, it can be manufactured by superimposing the other transparent electrode on this composite film, so that the manufacturing is easy and the number of steps can be reduced.

As a pair of transparent electrodes sandwiching the composite film, ITO (indium tin oxide) is formed on the surface of a transparent support such as glass, plastic film [eg polyethylene terephthalate (PET), polyether sulfone (PES)]. Examples thereof include those obtained by forming a transparent conductive film such as SnO ₂ or the like by vapor deposition, sputtering, etc., as well as transparent conductive glass and films used in ordinary liquid crystal display devices.

A suitable thickness of the composite film is usually 5 to 30 μm. In order to apply the above solution onto the transparent electrode, any conventionally known coating method such as a bar coating method, a spin coating method, a spray coating method or a roller coating method can be adopted.

[0028]

EXAMPLES The liquid crystal composite film of the present invention will be described below with reference to examples, but the present invention is not limited to the examples. Example 3-Hydroxymethyl-3-methyloxetane was reacted with 1-bromobutane according to a conventional method to give 3-butoxymethyl-3-methyloxetane. The reaction formula is shown below.

[0029]

[Chemical 4]

The product obtained was converted into BF ₃ O (C ₂ H ₅ ) ₂
Cationic polymerization was carried out in the presence of a catalyst to obtain a homopolymer (a). This product had _Mw of 300,000 and _Mw / _Mn of 1.05 in terms of polystyrene. On the other hand, 3-hydroxymethyl oxetane was reacted with a silylating agent (C ₂ H ₅ ) ₃ SiCl to protect the hydroxyl groups. The reaction formula is shown below.

[0031]

[Chemical 5]

The product obtained is BF₃O (C₂H_Five)₂
Cationic polymerization is carried out in the presence of a catalyst, followed by methanol.
Hydrolyze with a hydroxyl group to form a hydroxyl group as shown in the formula below.
A homopolymer (II) was obtained. This thing is a police
M in ren conversion_wIs 120,000, M _w/ M_nIs 1.2
It was

[0033]

[Chemical 6]

Then, 24 parts of the homopolymer (a) was added.
Parts, 6 parts by weight of homopolymer (b), and polyiso
Cyanate (Takeda Pharmaceutical Co., Ltd. product name A-10) is watered
Compounded in an amount equivalent to the acid group, liquid crystal material (Merck
70 parts by weight of E31LV manufactured by Bread Co., together with a solvent
It was dissolved in 560 parts by weight of dichloromethane. Got
Apply the solution on glass with transparent electrode by bar coating method
And dried for 1 hour at 100 ° C to form a liquid crystal composite with a thickness of 8 μm.
A film was obtained. Glass with another transparent electrode on this liquid crystal composite film
Were piled up to form an evaluation cell.Comparative example As a polymer to be mixed with the liquid crystal material, radical polymerization is used.
Resin (butyl acrylate / hydroxyethylmethac)
Relate = 80/20, M_w: 500,000, M_w/ M_nBut
Evaluation cell in the same manner as in Example except that 5.5) was used.
GotEvaluation test A spectrophotometer (made by Shimadzu) was used for each cell obtained in Examples and Comparative Examples.
UV-160) manufactured by Seisakusho Co., Ltd., 200Hz square wave
And voltage-transmittance characteristics (VT characteristics) were examined.
Around that time, the results shown in Table 1 were obtained. T in Table 1₀Applied voltage is 0V
Is the transmittance (%) when
0%), V₉₀Is the applied voltage when giving a transmittance of 90%
Pressure (V). Then, the contrast is expressed by the formula
(%) / T ₀(%) Was calculated and evaluated.

[0035]

[Table 1]

From the results shown in Table 1, the liquid crystal composite films of Examples are
It is understood that the contrast is higher than that of the comparative example and the V ₉₀ is small, so that low voltage driving is possible.

[0037]

As described above, the liquid crystal composite film of the present invention is a liquid crystal composite film composed of a polymer material composed of an ionic polymer of cyclic ether and a liquid crystal material, and therefore has a good phase separation structure. There is an effect that a film structure can be created and high contrast in a thin film can be achieved.

When an ionic polymer of a cyclic ether having at least a part of the polyoxetane skeleton is used as the polymer material, the polymer main chain has a flexible structure and the molecular weight is narrow and narrow. Having a distribution allows for more desirable phase separation. Further, since it is easy to introduce a polar group, it is expected to improve various characteristics such as increasing the dielectric constant and lowering the driving voltage. In particular, when a hydroxyl group-introduced and cross-linked polymer material is used as a polar group, high voltage and high voltage driving can be achieved.

Therefore, the liquid crystal composite film of the present invention can be suitably applied not only to a light control material but also to a high-definition display using a non-linear element.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kensaku Takada 1-3-1 Shimaya, Konohana-ku, Osaka Sumitomo Electric Industries, Ltd. Osaka Works

Claims (3)

[Claims] 1. A liquid crystal composite film comprising a polymer material composed of an ionic polymer of cyclic ether and a liquid crystal material. 2. The liquid crystal composite film according to claim 1, wherein the polymer material comprises an ionic polymer of a cyclic ether having a polyoxetane skeleton represented by the following general formula in at least a part thereof. [Chemical 1] (In the formula, R ¹ and R ² are the same or different organic groups, and n is the degree of polymerization.) 3. A polymer material obtained by crosslinking a polymer having a polyoxetane skeleton in which at least one of R ¹ and R ² is a group partially having a hydroxyl group with a crosslinking agent capable of reacting with the hydroxyl group. The liquid crystal composite film according to claim 2.